The present invention relates to a mold for a relatively tall-sided component that includes an in-mold decoration sheet. In particular, the present invention relates to such a mold for a component having a generally cylindrical wall, such as an electric meter face cover, where the in-mold decoration sheet forms at least a portion of the exterior of the cylindrical wall.
An electric meter or the like typically includes internal machinery and/or circuitry for metering electricity and a meter display for being read by a meter reader, a customer, etc. The meter display may be electronic or mechanical in nature. Especially in the case where the meter display is mechanical, such display typically protrudes from a meter housing, and therefore must be covered by a display cover that protects the display from external elements and that allows a meter reader, customer, etc. to read the display.
Typically, the display cover is generally cylindrical with opposing generally circular ends, where one end is closed and the other end is open. Thus, the display cover is mounted to the meter housing at the open end, the meter display protrudes from the meter housing into the display cover through the open end, and the display is read through the closed end. Although by no means definitive, a display cover may have an approximate cylindrical diameter of about 6 inches and an approximate cylindrical height of about 5 inches and has a wall thickness of about 0.1 to 0.12 inches.
Typically, the display cover is formed in a mold as a generally unitary body from an elastomeric or plastic material or the like such as a clear polycarbonate. In at least some instances, it is desirable as part of the molding process to include within the mold an in-mold decoration sheet so that the molded display cover includes the in-mold decoration sheet. For example, when molding the display cover from a clear polycarbonate, it may be desirable to include in the mold an opaque-tint UV-resistant in-mold decoration sheet that forms at least a portion of the cylindrical part of the molded display cover. Accordingly, the opaque-tint UVF-resistant decoration imparts the formed display cover with a UV-resistant cylindrical wall which can act to shade the meter display from exposure to the sun and to prevent dangerous heat build-up on the meter display from exposure to the sun. Of course, the in-mold decoration may also include words, pictures, decorative designs, logos, etc.
Owing to the general structure of the molded cover, the forming mold for such cover generally includes a female part generally corresponding to the exterior surface of the cover and a male part generally corresponding to the interior surface of the cover, where the male part is inserted within the female part such that the cover is molded therebetween. Accordingly, each of the male and female parts includes a generally cylindrical wall corresponding to and defining a cylindrical wall of the cover and a generally circular wall corresponding to and defining a circular end of the cover.
The in-mold decoration may be formed from any appropriate material. In the case of a UV-resistant opaque-tint decoration for a meter display cover, the material may be a polycarbonate similar to if not identical with the polycarbonate molded to form the remainder of the cover, although of course with a UV-resistant opaque tint. Such decoration is generally a strip having a width generally corresponding to the cylindrical height of the display cover and a length generally corresponding to the cylindrical circumference of the display cover such that the decoration is substantially coextensive with the cylindrical wall of the formed display cover. The decoration is flexible enough to be curved along the length thereof and inserted within the female part of the forming mold such that the decoration covers substantially the entire circumferential extent of the cylindrical wall of the such female part. With such decoration inserted, the male part of the forming mold is coupled to the female part to form a void, and the forming polycarbonate is appropriately introduced to the void to form the display cover.
Significantly, in the course of molding the display cover, the inserted decoration should be held closely to the cylindrical wall of the female part of the mold such that the introduced polycarbonate stays substantially on the side of the inserted decoration opposite the cylindrical wall of the female part (i.e., interior to the inserted decoration). The decoration should not be allowed to buckle or crumple within the mold such that the introduced polycarbonate migrates to the side of the inserted decoration facing the cylindrical wall of the female part (i.e., exterior to the inserted decoration). Otherwise, the migrating polycarbonate could stretch or tear the inserted decoration, resulting in color discontinuities or variations appearing in the finished display cover. As may be appreciated, such color discontinuities or variations are aesthetically displeasing at a minimum, and functionally impairing at a maximum.
To prevent such buckling and crumpling in the decoration as inserted in the female part of the mold, such decoration may be provided with a relatively short width, realizing that the likelihood of such buckling and crumpling increases with such width. However, a relatively short width may not be an available option, such as in the case of a meter display cover with a cylindrical diameter of about 6 inches and a cylindrical height of about 5 inches and an inserted opaque-tint UV-resistant decoration that should cover substantially the entire cylindrical height.
As an alternative, such decoration as formed may have a sufficient thickness to prevent such buckling and crumpling when inserted. However, it is likely the case that decoration cannot be too thick; otherwise, the migrating polycarbonate cannot flow past the interior of the decoration in the mold, or at least such polycarbonate will be too thin interior to the decoration. Moreover, if the decoration is too thick, such decoration will not be flexible enough to the degree necessary for being curved along the length thereof for insertion within the female part of the forming mold.
In fact, although buckling and crumpling is more likely, the decoration as formed should have a relatively minimal thickness, on the order of 0.008 to 0.012 inches, both to allow the migrating polycarbonate to flow past the interior of the decoration and to be flexible enough to the degree necessary for being curved along the length thereof for insertion within the female part of the forming mold. Moreover, and at any rate, a thinner decoration is less costly to produce, at least from a materials point of view.
To positively hold the inserted decoration closely to the cylindrical wall of the female part of the mold, the mold may be provided with an appropriate holding assembly that holds the inserted decoration in place during the molding process. Alternatively, the mold may be provided with an appropriate vacuum assembly that applies a negative pressure to hold the inserted decoration during the molding process. In either case such holding assembly or vacuum assembly adds excessive cost and complexity to the mold and molding process, and therefore to the molded display cover.
Note, too, that the inserted decoration may alternately comprise a polycarbonate or the like deposited by way of a vacuum or a spray onto the female part of the mold. Once again, though, the deposition technology adds excessive cost and complexity to the mold and molding process, and therefore to the molded display cover.
Accordingly, a need exists for a mechanism within the mold that holds the inserted decoration closely to the cylindrical wall of the female part of the mold, especially in the case where the cylindrical wall is relatively tall and the decoration is therefore relatively wide, so that the decoration does not buckle or crumple within the mold such that the introduced polycarbonate is allowed to migrate exterior to the inserted decoration. More particularly, a need exists for such a mechanism within the mold that is generally passive and simple and does not add excessive cost to the mold and molding process, and therefore to the molded display cover.
The present invention satisfies the aforementioned need by providing a mold assembly for accepting a generally flexible inserted decoration sheet and for molding a generally cylindrical component to include the inserted decoration sheet. The component also includes a cylindrical wall and a closed end.
The mold assembly has a female part generally corresponding to an exterior surface of the component and a male part generally corresponding to an interior surface of the component. The male part is insertable within the female part such that the component is molded therebetween from an introduced mold material.
The female part includes a generally circular wall corresponding to and defining the closed end of the component, a generally cylindrical wall corresponding to and defining the cylindrical wall of the component, and a pair of demarcating ridges on the cylindrical wall of the female part. The pair of ridges accept the inserted decoration therebetween and hold the inserted decoration against the cylindrical wall of the female part. In the course of molding the component to include the inserted decoration, the pair of ridges hold the decoration closely to the cylindrical wall of the female part such that the introduced mold material stays substantially on a side of the inserted decoration opposite the cylindrical wall of the female part.